Conventionally, removable fin systems were developed to allow users to replace fins when broken, experiment with different types of fins, and provide ease in transporting the watercraft when the fins where removed. However, conventional removable fin systems often create rigidity through the tail of the watercraft that impede longitudinal and torsional flex, while at the same time weakening the overall structure by creating shear points in the board. Furthermore, the fins themselves can become loose over time and cause water leakage due to poor adherence of the fin box to the body of the board. Accordingly, the need exists for alternative approaches that effectively provide flex and strength. The present invention is directed to an improved fin system that provides increased strength of mechanical bond between the fin and board while enhancing the flexibility of the watercraft body.